This paper presents a simple prototype of a metasurface-based on-chip antenna operating in 0.3-0.32THz. The proposed structure is constructed from two layers of polyimide-substrates with thickness of 0.1mm that sandwich a middle metallic ground-plane layer of 50-micron thickness. A series of linear slots of varying lengths are etched on the radiation patches of the top-layer to create a metasurface. This is shown to enhance the antenna's effective aperture area that improves its radiation performance without affecting the overall antenna's footprint. To reduce the surface-waves and substrate-losses a meander-line slits has realized inside the ground-plane. The antenna is fed by an open-ended microstrip feedline located on the bottom-layer. The feedline consists of threebranches that are aligned under each radiation patch to achieve the maximum electromagnetic (EM) transfer from bottom-side of the bottom layer to the topside of the toplayer. Coupling of the EM energy from the bottom-layer to the top-layer is via meander-line slits introduced between the two layers. Simulation results show improvement in the antenna's impedance bandwidth, gain and efficiency.